Telegraph system



Dec. 20, 192 7.

c. s. DEMAREST TELEGRAPH SYSTEM Filed June 2 1924 INVENTQR 6 Jlfiemwmst A TTORNE Y Patented Dec. 7 20, 1927.-

. UNITED, T E T CE cnARtEs s. nnMARns r, or nrnenwoon, new annsnmnssxenon r nivrnnroanrnnn j rnonnnnn TELEGRAPH cor/many, A. conroaamoiv or X I rE'LEe RArn .sysrnm. I i- Application filed June 28 an impulse of alternating current is converted into an equivalent direct current'impulse for actuating direct currentIapparatus at a repeater or a receiving station.

As is well known, it is desirable to em-{ I and by the condenser 12 so as' to be resonant I I ploy alternating currents for the transmissionof signals, but in order to receive such losignals it -is customary to convertthe trans mitted signals into equivalent direct current signals.

The object of this invention is to provide a-simple and reliable mechanism for translating the impulses of alternating current into equivalent direct current impulses and caus'ingthe latter impulses to operate direct current telegraph apparatus. I This invention will be clearly understood from the following description when read in connection with the attached drawingof which Figure 1 shows schematically a simple form of embodiment of the invention; Fig. 2 shows the application of the invention 12$ for two-waysignaling; and Fig. 3 shows'an,

embodiment ofthe invention for receivingradiofrequency signals,-

' In Fig.1, statiomA 1s a tus'at. station A comprises a key 1 and a; generator .2 capable of producing the alter-, natingicurrent by means of which the sig nals are transmitted over the line 3; ,Con-

' nectedwiththe receiving end of this line. is

an alternating current relay L of a type shown in the copending applications of Thompson, Serial Nos. 525,7 27 and 525,728,

filed December 29, 1921. I This relay is high ly sensitive and selective being tuned. me-

. chanically to resonate at the desired fre quency, say, 1,000 cycles, and the circuit is also tuned for this frequency. The armature 5 of this relay is connected with the winding of relay 6, the connection including the resistances 7 and 8. The armature 5 is grounded, and the winding-of relay 6 is connected with thebattery 9. A condenser 10 is connected in parallel with the winding of relay 6 and the resistance 8. The contact of relay "'6 is connected .with the winding of a direct current telegraphrelay or sounder 11. The manner in which this circuit operates is as follows:

and will close its contact whenever the relay transmitting tion and station B a receiving station. I For the sake of simplicity,-transmitt1ng app-ara Wheneverthe key 1 is closed a trainof 1924. Serial Ito. 723,009.

waves of the frequency of I duced by the generator 2 will be impressed-9 upon the line 3 and transmitted to the: re -v ceivingstation. This frequency lying with-I; in the voice range will'be readily-trans. mitted over the said line The receiving cir'a cuit is tuned by the windingsfof relay 4:

tact at the rate of=1,000 times persecond.

Accordingly, a circuit .will be established from the battery 9 throughthej winding of relay 6'and resistances 8 and-7 and the 0011- tact of relay 5. to groundeachand every 1 time the armature of the [relay touches its contact. Furthermore, the condenser 10 will be chargedv each. time this circuit is closed. The armature of relay 6 will beattracted,

is energized, and by properly proportioningv the constantsofthe condenser 10, the 'resistance; 8 and the winding of relay .6, sufiicient current will *flow' from the condenser" through the windingj-to hold the armature 'ofrelay 6 attracted during theintervalin which the armature 5 is. away fromits con; tact. Whenever the armature of relay 6. closes its contact, current'will flow from the'battery 13 through the windingofpthe 1 telegraph relay or sounder 1 1 and willacg cordin'gly attract the armature thereof. This armature will remain attracted as long as the impulseof alternating current continues to flow through the windings of relay 4, viz, as long as the key lat station A' re I I mainsclosed; I It willbe seen, therefore, that. I

by means otthe arrangement shown schematically this figure, it ispracticableto I mission. This is efiected by transmitting at 5 one frequency in one direction and at a dlfferent frequency in the opposite direction. 11o

70 I 7' i be set in vibration and willftouchitseo s,

23 by means of 'the transformerQS, but it'- ist'o be understood that-other well known- Thus, for example, the generator 20 at est-a tionA might produce a frequency of 1,000

cycles While the generator 21 at station B might produce. a frequency 1,100 cycles. The transmitting 22 at station A is connected With the apexof the bridge arms one of which is connected With the line and the other With the artificial line The receiving circuit at station his repre sented as beingconnected across the arms means of connecting maybe employed with out varying the scope of the invention.

The

relay 27 is connected with the secondary Winding of transformer 26, and the circuit of these Windingsis tuned by means of the condenser 28. This-circuit, comprising the secondary oftra nsformer 26, tlie' windings of-relay 27xandjthe condenser 28,-1s'tuned for the reception of 1,100 cycles. The -ar-' mature 29 of thisre'lay is connected with are-similar they need not be further dethe Winding of relay'SO in the same manner in which the armature 5 of relay f was connected in Flgpl, and since these details scribed. The receiving circuit at stationxB is similar to that'at station A except" that the circuit embracing-"the winding ofrelay 32,- the secondary of transformer 33 and the condenser 8% is tuned to the frequency of a 1,000 cycles. i a I V When an impulse! of 1,100 cycles is trans V mitted from station B by the closing of key 35, relay-27 at station-A' will be energized since the circuit'of the windings of this re-"' lay is tuned to "this frequency. The arma 'ture29 of thisrelay Willfvibrate-at the "im 7 V pressedfreque'ncy and will cause the opera tion of relay 30 Which-Will remain ener V giz 'ed so long'as this impulse of alternating currentcontinuesto energize relay Qi-and will transmit a direct current impulse to the direct current *receiving, apparatus, the length of which impulse is equal 'to the length of the alternatingcurrent inipulsei By the'operation of key 2:2 an impulse of alternating current of-l,000 cycles will be impressed upon the line '24 and will operate' the alternating current relay gil at station B which Wlll effect the transmission of a direct current impulse 1n the same'manner as described above. Since the frequencies of transmission are different, and since the :transmitted frequencies are applied to the apex of the bridge arms, the receiving apparatus' atstations A and B Will not be affected by the signals transmitted from the same stations. Y

The arrangement shown in 3-illustrates the application of this invention to a radio system; If an impulse of 'radio fre quency,-modulated, for example, by an 1m,

pulse of 1,000 cycles, is impressed upon the antennai'aO, current will be setup in. the

length of the alternatingfcu tuned circuit ll which will impress a cor-; e

responding potential up-on the detector The resultant detected signal of 1,000 cycles v ll be, impressed by the transformer uponthe circuit ofthe relayed, 'W'hich is tuned by meansbf the condenser 45 for 1,000 cycles. The armature of this relay will vibrate at this frequency and will effeet the operation 'ofrelay 4;? Which in turn will transmit a direct currentimpulse the length or; which will be proportional 'to the ent impulse actuatingthe alternating curl nt relay i l;

This same circuit is applicable to thefdethat it is capable of embodiment in other.

forms ithout departing from the spirit and scope of the" appended claims;

What is claimed isz 7' 1. In a-telegraph-systemgt 1e combination With line of a sourceof-alternatingcurrent",-means for applying to thejsaid line inipulses of the said alternating current repre-: sei iting dots and dashes, anda'receiving circuit having an alternating currentvi'relay mechanically and electrically tuned to the frequency of "the said alternating current, and a direct currentzrelay so controlled by:

the operation of the said alternating current relay that the armature of the direct current' relay will be attracted during the time in which the armature of-the alternating. cur-.

rent relay'vibrates;

2. In a telegraphsystem, theco'mbination' with alternating current relay: mechanically and electricallytuned to a definite frequency ofza direct current relay controlled by the said alternating current relay and having means to. transmit direct current impulses eorresponding to the 'alternatingrcurs re ntimpulses actuating the said alternating current relay, g

-'3; In a telegraph system, the combination with an. alternating current relay of means to tune toa'deiinite frequency the circuit containing the windings-thereof, the arma- I ture of the said'relay having a natural periodof vibration equal to theresonant frequency of the circuitof the windings thereof, a di-: rect current relay,ihev Winding'of which is, connected with the armature of. the alternating current may and having :a condenser connected in parallel with the said inding of such magnitude as to maintain the energization of the said relay during the time in which the armature of the alternating current relay is away from the contact connected with the winding of the said direct current relay so that the direct current relay remains energized substantially as long as the alternating current wave continued to operate the alternating current relay, and" signal indicating means controlled by the said direct current relay.

4. In a telegraph system, the combination with a line over which signals, consisting of trains of unmodulated waves, are trans-,

mitted of a highly sensitive alternating our 15 rent relay whose winding circuit is tuned to June, 1924; l r CHARLES s. DEMAREST.

thefrequency of the said waves and Whose is such as to maintain the direct current relay energized during the interval in which the alternating current armature is away from the contact connected with the direct current relay. r

In testimony whereof, I have signed my i name to this specification this 27th .da'y of 

